Field of the Invention
The invention relates to a rotatable operating member and an electronic device having the same, and in particular to a technique for detecting rotation of an operating member which an electronic device has.
Description of the Related Art
An electronic device is equipped with various operating members such as a pushbutton type, a sliding type, and a rotary type so as to implement various processes and operations. A variety of sensors are used as means for detecting operation of such operating members when they are operated. For example, a technique for detecting rotation of a rotatable ring, which is an exemplary rotary operating member, using photo-reflectors has been proposed (see Japanese Laid-Open Patent Publication (Kokai) No. 2007-64665).
Specifically, reflective surfaces with different reflectivities are alternately provided at intervals of predetermined rotation angles on a rotatable ring, and when the rotatable ring is operated, photo-reflectors are selectively turned on and off (light is received/light is not received). As a result, rotation of the rotatable ring is detected. Here, ways to provide reflective surfaces with different reflectivities on the rotatable ring include a way in which reflective surfaces are directly formed on an inner peripheral surface of an annular member, and a way in which reflective sheets are attached to an inner peripheral surface of an annular member.
However, if a rotatable ring is manufactured by directly forming reflective surfaces with different reflectivities on an annular member, a problem of increasing manufacturing (machining) costs will arise. On the other hand, when a rotatable ring is manufactured by attaching reflective sheets to an annular member, manufacturing costs are reduced as compared to the case where reflective surfaces are directly formed on an annular member. However, for a rotatable ring that is able to make a 360-degree turn, it is necessary to attach reflective sheets to an inner peripheral surface of an annular member over the whole circumference. On this occasion, if a minuscule gap is formed at a joint between the reflective sheets, or if there is a minuscule overlap at a joint of the reflective sheets, variations in reflectivity are not regular, and this may cause causes false detection when a rotation angle is detected.